Method and apparatus for preparing high purity hydrogen bromide

ABSTRACT

A method and apparatus for preparing high purity hydrogen bromide, wherein a starting hydrogen bromide which contains impurities having low boiling points is supplied to an intermediate space. While the gas phase of the starting hydrogen bromide is allowed to ascend through an upper rectifying section, it is brought into contact with a first reflux solution flowing in the reverse direction. The uncondensed gas stored in an upper space is cooled and partly condensed. The condensed liquid is allowed to flow down through an upper rectifying section as the first reflux solution. The liquid-phase of the starting hydrogen bromide is mixed with the first reflux solution in the intermediate space and serves as a second reflux solution. The liquid stored in a lower space is heated and partly evaporated. The liquid stored in the lower space is supplied outside as high purity hydrogen bromide. The uncondensed gas stored in the upper space is discharged outside.

TECHNICAL FIELD

The present invention relates to a method and apparatus for preparinghigh purity hydrogen bromide (HBr).

BACKGROUND ART

Hydrogen bromide has been used in etching and others of a semiconductormanufacturing process in place of fluorocarbon gases whose influence onthe ozone layer has been questioned and whose utilization is regulated.Hence, there is a demand for developing the technique of preparing highpurity hydrogen bromide in a large amount.

An example of a conventional method for preparing high purity hydrogenbromide will be described with reference to FIG. 2. In a cylinder 1, araw material consisting of hydrogen bromide and impurities is stored.The raw material is evaporated by heating the cylinder 1. The hydrogenbromide gas thus generated is adjusted to a predetermined pressure bymeans of a pressure regulating valve 2 and introduced into an adsorber 3filled with molecular sieves. By virtue of the molecular sieves, theimpurities other than moisture contained in the gas are removed then thegas is fed to a drier 4 filled with a desiccant to remove the moisture,thereby purifying the hydrogen bromide gas. The hydrogen bromide gasthus purified is introduced into a product cylinder 5. Subsequently thehydrogen bromide gas is cooled by a refrigerant 6 which is a mixture ofdry ice and ethyl alcohol, condensed, and stored in the product cylinder5.

However, in the method for purifying hydrogen bromide mentioned above,the molecular sieves gradually deteriorates with the passage ofoperation time of the apparatus. So does the purity of the product. Tomaintain the purity of a product at a predetermined level, molecularsieves must be replaced frequently. Hence, the aforementioned purifyingmethod is not suitable for preparing high purity hydrogen bromide in alarge amount.

DISCLOSURE OF INVENTION

The present invention is intended to provide a method and apparatuscapable of preparing high purity hydrogen bromide continuously in alarge amount.

A method for preparing high purity hydrogen bromide according to thepresent invention comprises the steps of:

providing a rectifying column composed of

a lower space,

a lower rectifying section,

an intermediate space,

an upper rectifying section, and

an upper space,

which are positioned in the order mentioned from the bottom toward thetop;

supplying a raw material consisting of hydrogen bromide and impuritieshaving boiling points lower than that of hydrogen bromide, into theintermediate space;

allowing a gas phase of the supplied raw material to ascend through theupper rectifying section while the gas phase is brought into contactwith a first reflux solution flowing down from the top, leading thegas-phase to the upper space, and storing an uncondensed gas in theupper space;

cooling the uncondensed gas stored in the upper space, therebycondensing part of the uncondensed gas;

allowing the liquid thus condensed to serve as the first reflux solutionand to flow down through the upper rectifying section to theintermediate space;

mixing the liquid phase of the supplied raw material with the fistreflux solution in the intermediate spacer thereby making a secondreflux solution, and allowing the second reflux solution to flow downthrough the lower rectifying section to the lower space and then storinga liquid in the lower space;

heating the liquid stored in the lower space to evaporate part of theliquid and allowing the gas generated to contact with the second refluxsolution which flows down from the top while ascending through the lowerrectifying section; and

discharging the liquid stored in the lower space outside in the form ofhigh-purity hydrogen bromide, simultaneously discharging the uncondensedgas stored in the upper space outside.

A temperature of cooling the uncondensed gas in the upper space ispreferred to fall within the range of -30° C. to -50° C. On the otherhand, a temperature of heating the solution stored in the lower space ispreferred to fall within the range of -15° C. to -20° C.

The apparatus for preparing high purity hydrogen bromide, employed inthe aforementioned method, comprises:

a rectifying column comprising a longitudinal pressure vessel which isdivided into,

a lower space,

a lower rectifying section in which plural stages of rectifying platesare disposed,

an intermediate space,

an upper rectifying section in which plural stages of rectifying platesare disposed,

and an upper space which are positioned in the order mentioned from thebottom toward the top;

means for supplying a raw material consisting of hydrogen bromide andimpurities having boiling points lower than that of hydrogen bromide,into the intermediate space;

a first heat exchanger for cooling and condensing part of the gas storedin the upper space;

a second heat exchanger for heating and evaporating part of the liquidstored in the lower space;

means for discharging gas stored in the upper space outside therectifying column in the form of gas rich in impurities; and

a product take-out means for taking out the liquid stored in the lowerspace outside the rectifying column in the form of high purity hydrogenbromide.

Hereinbelow, we will describe a process for purifying hydrogen bromideusing the purification apparatus of the present invention.

Raw material consisting of hydrogen bromide and impurities havingboiling points lower than that of hydrogen bromide, is supplied to theintermediate space in the form of a gas-liquid mixture. The gas phasecontains impurities in a relatively large amount; in contrast, theliquid phase contains impurities in a relatively small amount.

The gas phase of the raw material ascends through the upper rectifyingcolumn. In the upper rectifying column, hydrogen bromide liquidcontaining a relatively small amount of impurities flows down as a firstreflux solution. Therefore, the gas phase comes into contact with thefirst reflux solution flowing in the reverse direction. Owing thiscontact, a component of the gas phase having a high boiling point,namely, hydrogen bromide is condensed and incorporated into the firstreflux solution. On the other hand, components having low boilingpoints, namely, impurities, contained in the first reflux solution, areevaporated. The gas stored in the upper space is cooled by the firstheat exchanger and partly condensed. By setting the cooling temperatureto an appropriate condition such as a temperature from -30° C. to -50°C., it is possible to reduce the content of impurities of the condensedliquid. The condensed liquid is returned to the upper rectifying sectionand then flows down through the rectifying section as the first refluxsolution. As a result, the uncondensed gas is stored in the upper space,while hydrogen bromide liquid containing impurities in a relativelysmall amount, is stored in the intermediate space. The uncondensed gasrich in impurities is discharged outside the upper space.

On the other hand, the liquid phase of the raw material is mixed, in theintermediate space, with the first reflux solution flowing from theupper rectifying section. The resulting mixture solution flows downthrough a lower rectifying section as a second reflux solution andstored in the lower space. In the lower space, the stored liquid, thatis high purity hydrogen bromide as will be described later, is heatedand partly evaporated by a second heat exchanger. By setting the heatingtemperature to an appropriate condition such as -15° C. to -20° C., thecontent of impurities in the stored liquid can be reduced. The generatedgas ascends through the lower space and comes into contact with thesecond reflux solution flowing in the reverse direction. Consequently,hydrogen bromide of the gas phase is condensed and incorporated into thesecond reflux solution; on the other hand, the impurities contained inthe second reflux solution is evaporated. As a result, high purityhydrogen bromide liquid is stored in the lower space. The high purityhydrogen bromide liquid is taken out and recovered as a product.

The first heat exchanger may be disposed either outside or inside theupper space. In the case where the first heat exchanger is disposedoutside, uncondensed gas stored in the upper space is introduced intothe first heat exchanger and partly condensed by exchanging heat with arefrigerant. Thereafter, the produced liquid is returned to the upperspace and remained uncondensed gas is discharged outside. In the casewhere the first heat exchanger is disposed inside the upper space, partof the uncondensed gas is condensed by exchanging heat with arefrigerant, in the upper space. On the other hand, the other part ofthe uncondensed gas is discharged outside from a portion in the vicinityof the top of the upper space.

The second heat exchanger is desirably disposed outside the lower space.In this case, the liquid stored in the lower space is introduced intothe second heat exchanger and partly evaporated by exchanging heat withthe atmosphere. Thereafter, the generated gas is returned into the lowerspace.

By this procedure, the temperature and pressure of the lower space aresuccessfully controlled and mainly impurities of the liquid stored inthe lower space are evaporated, with the result that the purificationdegree of hydrogen bromide contained in the liquid is increased.

Furthermore, it is desirable to dispose a third heat exchanger insidethe lower space in addition to the second heat exchanger. In this case,the raw material supply means is used for supplying the raw material tothe intermediate space by way of a flow passage located on the heatingmedium side of the third heat exchanger.

The raw material is thereby successfully cooled to a predeterminedtemperature and supplied to the intermediate space.

It is preferred that a storage tank is disposed outside the rectifyingcolumn. In this case, liquefied high-purity hydrogen bromide stored inthe lower space is transferred to the storage tank by the producttake-out means and stored therein.

In this case, a hydrogen bromide gas is cooled to a temperature from-15° C. to -20° C. and condensed by disposing the heat exchanger on alevel higher than the inner surface of the liquid stored in the storagetank.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1: A block diagram showing an embodiment of the apparatus forpreparing high purity hydrogen bromide according to the presentinvention.

FIG. 2: A block diagram showing an embodiment of an apparatus forpreparing high purity hydrogen bromide in the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows an example of a block diagram of the apparatus forpreparing the high purity hydrogen bromide according to the presentinvention.

The apparatus is mainly composed of the following three portions: araw-material supply section 10, a rectifying column 20, and a productstorage tank 30. Furthermore, the apparatus comprises additionalequipments such as a refrigerator 40, a detoxifying apparatus 45, andpipes and valves. The rectifying column 20 is housed in a thermalinsulation container 28 together with the additional equipments.

The raw-material supply section 10 comprises; a cylinder 15 for storinga raw material consisting of hydrogen bromide and impurities havingboiling points lower that of hydrogen bromide; a heater 16 accommodatingthe cylinder 15 for heating the raw material 11; and a pressureregulating valve 80 connected to the top portion of the cylinder 15. Thepressure regulating valve 80 is connected to the rectifying column 20 byway of a pipe 51.

The rectifying column 20 is constructed by layering the following fiveportions consecutively from the bottom, thereby forming a singlepressure vessel 21 as a whole. A lower space 26 is formed between thebottom of the pressure vessel 21 and the lower surface of a lowerrectifying section 25. The lower rectifying section 25 is formed bydisposing plural stages of rectifying plates. An intermediate space 24is formed between the upper surface of the lower rectifying section 25and the lower surface of the upper rectifying space 23. The upperrectifying section 23 is formed by disposing plural stages of rectifyingplates. An upper space 22 is formed between the top portion of thepressure vessel 21 and the upper surface of the upper rectifying section23.

Inside the lower space 26, a third heat exchanger 73 is disposed. Theinlet-side of the heating medium of the third heat exchanger 73 isconnected to a raw-material supply section 10 by way of a pipe 51 and apressure regulating valve 80. On the other hand, the outlet side thereofis connected to the intermediate space 24 of the rectifying column 20 byway of a pipe 52 and an expansion valve 81.

Furthermore, onto the outside of the lower space 26 is connected asecond heat exchanger 72 using the atmosphere as a heat source. Theinlet side of the cooling medium of the second heat exchanger 72 isconnected to a portion in the vicinity of the bottom of the lower space26. On the other hand, the outlet side thereof is connected to a portionin the vicinity of the top of the lower space 26 by way of a pipe 55 anda pressure regulating valve 82. It should be noted that the second heatexchanger 72 is disposed outside the heat insulation container 26 at alevel lower than that of a predetermined liquid surface of the lowerspace 26.

To the portion lower than the predetermined liquid surface of the lowerspace 26 is connected a pipe 53 for taking out liquid (liquefied highpurity hydrogen bromide). The pipe 53 is connected to a portion in thevicinity of the top of the product storage tank 30 by way of a pressureregulating valve 84. To the lower space 26, a liquid level gauge 27 isattached.

Inside of the upper space 22, a first heat exchanger 71 is disposed. Theinlet side of the cooling medium of the first heat exchanger 71 isconnected to a refrigerator 40 by way of a pipe 63 and an expansionvalve 87. On the other hand, the outlet side thereof is connected to therefrigerator 40 by way of a pipe 64. It should be noted that the firstheat exchanger 71 may be provided outside the upper space 22.

To the top portion of the upper space 22 is connected a pipe 56 fordischarging the gas (uncondensed gas mainly composed of impurities)stored in the top portion. The pipe 56 is further connected to adetoxifying apparatus 45 by way of a pressure regulating valve 83, aheater 76 and a pipe 57.

A product storage tank 30 is a thermal insulation container the outsideportion of which is covered with an insulating layer.

Above the liquid surface in the product storage tank 30, a heatexchanger 74 is disposed. The inlet side of the cooling medium of theheat exchanger 74 is connected to the refrigerator 40 by way of a pipe65 and an expansion valve 88. The outlet side thereof is connected tothe refrigerator 40 by way of a pipe 66.

Onto the outside of the product storage tank 30 is connected a heatexchanger 75 using the atmosphere as a heat source. The inlet side ofthe cooling medium of the heat exchanger 75 is connected to a portion inthe vicinity of the bottom of the product storage tank 30 by way of apipe 59. On the other hand, the outlet side thereof is connected to aportion in the vicinity of the top of the product storage tank 30 by wayof a pressure regulating valve 85.

To the bottom of the product storage tank 30 is connected a pipe 58 forsupplying a product (liquefied high-purity hydrogen bromide) outside.

The top portion of the product storage tank 30 is connected to thedetoxifying apparatus 45 by way of a pipe 61, a relief valve 86, and aheater 77.

Hereinbelow, we will explain a process for preparing high purityhydrogen bromide using the rectifying column shown in FIG. 1. Table 1shows a typical formulation of a raw material consisting ofsubstantially hydrogen bromide used herein. The raw material consists of97.96 vol % of hydrogen bromide and impurities including hydrogen (H₂),hydrochloric acid (HCl), methane (CH₄), nitrogen (N₂), carbon dioxide(CO₂), carbon monoxide (CO) and the like whose boiling points are lowerthan that of hydrogen bromide. It should be noted that the content ofmoisture (H₂ O) is 2 ppm or less.

                  TABLE 1                                                         ______________________________________                                        Composition Examp1e of Raw Material                                           Hydrogen Bromide (HBr)                                                                     Contents    Boiling Points                                       Components   (vol ppm. vol %)                                                                          at 1 atm (°C.)                                ______________________________________                                        H.sub.2      17,000  vol ppm -252                                             N.sub.2      50              -196                                             CO           42              -192                                             Ar           1               -185                                             O.sub.2      1               -183                                             CH.sub.4     65              -162                                             C.sub.2 H.sub.6                                                                            2               -89                                              HCl          3,200           -85                                              CO.sub.2     44              -78                                              H.sub.2 O    <2              +100                                             HBr          97.96   vol %   -67                                              ______________________________________                                    

The raw material stored in the cylinder 15 in a liquid state is heatedby the heater 16, evaporated into a gas having a pressure ofapproximately 20 kg/cm² G at a temperature of approximately 35° C. Thegas is then introduced into the heating medium side of the third heatexchanger 73 disposed inside the lower space 26. Subsequently, the gasis cooled by exchanging heat with liquid (liquefied high purity hydrogenbromide) stored in the lower space 26. The resultant gas is introducedin the expansion valve 81. Thereafter, it is adiabatically expanded andintroduced into the intermediate space 24 in the form of gas-liquidmixture having a pressure of approximately 8 kg/cm² at a temperature ofapproximately -20° C. The loading amount of the raw material used inthis example is set to 1000 Nm³ /h. In the gas phase of the raw materialintroduced in the intermediate space 24, impurities are contained in arelatively large amount and in the liquid phase, the impurities arecontained in a relatively small amount.

The gas phase of the raw material ascends through the upper rectifyingsection 23. In the upper rectifying section 23, a first reflux solution,namely, hydrogen bromide containing a relatively small amount ofimpurities flows down from the top. Therefore, the current of the gasphase comes into contact with the first reflux solution reverselyflowing. Owing to the contact, a component having a high boiling point,namely, hydrogen bromide contained in the gas-phase is condensed andincorporated into the first reflux solution. On the other hand,components having low boiling points, namely, impurities contained inthe reflux solution are evaporated.

In the upper space 22, the stored gas is cooled to a temperature from-30° C. to -50° C. by the first heat exchanger 71. As a result, mainlyhydrogen bromide in the gas is condensed. Thus, most of the condensedliquid is hydrogen bromide which includes a small amount of impuritieshaving low boiling points.

The condensed liquid is returned to the upper rectifying section 23 andthen flows down as the first reflux solution through the section 23.

As a result, the uncondensed gas rich in impurities is stored in theupper space. The hydrogen bromide liquid containing a relatively smallamount of impurities is stored in the intermediate space.

The uncondensed gas rich in impurities is led from the upper space 22 tothe detoxifying apparatus 45 by way of the pressure regulating valve 83and the heater 76.

In the detoxifying apparatus 45, hydrogen chloride, hydrogen bromide andcarbon monoxide contained in small amounts are removed from theuncondensed gas, the resultant uncondensed gas is discharged outside.

In the case of the formula shown in Table 1, if a loading amount of theraw material is set to 1000 Nm³ /h, the amount of the uncondensed gasthus discharged will be 69 Nm³ /h.

On the other hand, in the intermediate space 24, the liquid-phase of theraw material is mixed with the first reflux solution flowing from theupper rectifying section 23. The mixture solution flows down as thesecond reflux solution through the lower rectifying section 25 andstored in the lower space 26.

The liquid stored in the lower space 26, that is high purity hydrogenbromide as will be described later, is heated by the second heatexchanger 72 and third heat exchanger 73 to a temperature from -15° C.to -20° C. Then, a small amount of impurities contained in the liquid isevaporated together with hydrogen bromide.

The second heat exchanger 72 disposed outside the lower space 26 has afunction of controlling an inner temperature and pressure of the lowerspace 26. Since the second heat exchanger 72 is disposed at a levellower than a predetermined liquid surface of the lower space 26, theliquid stored in the lower space is led to the second heat exchanger 72by gravity. The liquid is warmed therein, partly evaporated and returnedto a portion in the vicinity of the top of the lower space. Therefore,the liquid can be automatically circularized by means of the heatexchanger 72, pipe 55 and pressure regulating valve 82, alone. In otherwords, a pump or the like is not required to circularize the liquid.

The generated gas ascends through the lower rectifying section 25 andcomes into contact with the second reflux solution flowing in thereverse direction. The hydrogen bromide contained in the gas phase iscondensed and incorporated into the second reflux solution. On the otherhand, impurities present in the second reflux solution are evaporated.

The condensed gas ascending to the intermediate space 24 is mixed withthe gas phase of the raw material and further ascend through the upperrectifying section 23 in the same manner as mentioned above.

As a result, liquefied high purity hydrogen bromide (99.9999%) is storedin the lower space 26.

The liquefied high purity hydrogen bromide is taken out as a productfrom the lower space 26 and allowed to pass through the pipe 53 and thepressure regulating valve 84 and then stored in a product storage tank30 placed outside.

In the case of the formula show in Table 1, if a loading amount of theraw material is set to 1000 Nm³ /h, the amount of the high-purityhydrogen bromide thus purified is 931 Nm³ /h in terms of a gas volume.

In the product storage tank 30, a temperature of the liquefied highpurity hydrogen bromide is approximately -20° C. and a pressure thereofis approximately 8 kg/cm² G. The relative relationship with the pressurein the rectifying column in this example is as follows: the pressure ofthe lower space 26 is higher than that of the intermediate space 24 byabout 0.3 kg/cm² and the pressure of the product storage tank 30 islower than that of the lower space 26 by about 0.5 kg/cm².

The liquefied high purity hydrogen bromide is derived from the bottomportion of the product storage tank 30, allowed to pass through the pipe58, and supplied, as a product, into a consuming equipment (not shown inthe figure).

The heat exchanger 75 connected onto the outside of the product storagetank 30 is used for heating the liquefied hydrogen bromide introducedfrom the product storage tank 30 by exchanging heat with the atmosphere.The generated gas is allowed to pass through the pressure regulatingvalve 85 and returned to a portion in the vicinity of the top of theproduct storage tank 30. This passage line is used for controlling thepressure of the tank when the liquefied hydrogen bromide is expelledout.

The heat exchanger 74 disposed at a level higher than the liquid surfaceinside the product storage tank 30 is used for cooling and condensinghydrogen bromide gas generated in the tank, thereby regulating atemperature and pressure of the tank.

Furthermore, the relief valve 86 connected to the top of the productstorage tank 30 is used for discharging the vapor of the tank outside byway of a heater 77 and a detoxifying apparatus 45 in case of excessivepressure increase in the product storage tank.

In this embodiment, to use the latent heat and sensible heat of astarting hydrogen bromide as a heat source for heating the liquid storedin the lower space 26, the third heat exchanger 73 is disposed in thelower space 26. The raw material is allowed to pass through the thirdheat exchanger and introduced into the intermediate space 24. However,the present invention is not limited to this embodiment. The lower space26 can be heated by the second heat exchanger 72 alone. In this case,the starting hydrogen bromide gas can be introduced directly from theraw material supply section to the intermediate space 24.

As mentioned in the foregoing, in the method and apparatus for preparinghigh purity hydrogen bromide of the present invention, since hydrogenbromide is purified by using two-stage rectifying column, impuritieshaving boiling points lower than that of hydrogen bromide can be removedwithout failure. As a result, liquefied hydrogen bromide having a puritydegree of 99.9999% can be prepared continuously in a large amount.

We claim:
 1. A method for preparing high purity hydrogen bromide, whichcomprises:(a) providing a rectifying column, comprising:a lower space, alower rectifying section, an intermediate space, an upper rectifyingsection, an upper space, which are positioned in the order mentionedfrom the bottom toward the top; (b) supplying a raw material consistingof hydrogen bromide and impurities having boiling points lower than thatof hydrogen bromide, into the intermediate space; (c) allowing a gasphase of the supplied raw material to ascend through the upperrectifying section while said gas phase is brought into contact with afirst reflux solution flowing down from the top, leading said gas phaseto said upper space, and storing an uncondensed gas in said upper space;(d) cooling said uncondensed gas stored in said upper space, therebycondensing part of said uncondensed gas; (e) allowing the liquid thuscondensed to serve as said first reflux solution and to flow downthrough the upper rectifying section to the intermediate space; (f)mixing the liquid phase of said supplied raw material with said firstreflux solution in the intermediate space, thereby making a secondreflux solution, and allowing said second reflux solution to flow downthrough said lower rectifying section to said lower space and thenstoring a liquid in said lower space; (g) heating the liquid stored insaid lower space to evaporate part of said liquid and allowing the gasgenerated to contact with said second reflux solution which flows downfrom the top while ascending through said lower rectifying sections; and(h) discharging said liquid stored in said lower space outside in theform of high-purity hydrogen bromide, simultaneously discharging saiduncondensed gas stored in the upper space outside.
 2. The method ofclaim 1, wherein said uncondensed gas stored in said upper space iscooled to a range of within -30° C. to -50° C., and said solution storedin said lower space is heated to a temperature of from about -15° C. to-20° C.
 3. An apparatus for preparing high hydrogen bromide,comprising:a rectifying column, comprising a longitudinal pressurevessel which is divided into a lower space, a lower rectifying sectionin which plural stages of rectifying plates are disposed, anintermediate space, an upper rectifying section in which plural stagesof rectifying plates are disposed, and an upper space, which arepositioned in the order mentioned from the bottom toward the top; meansfor supplying a raw material consisting of hydrogen bromide andimpurities having boiling points lower than that of hydrogen bromide,into said intermediate space; a first heat exchanger for cooling andcondensing part of an uncondensed gas stored in said upper space; asecond heat exchanger for heating and evaporating part of a liquidstored in said lower space; a means for discharging gas stored in saidupper space outside the rectifying column in the form of gas rich inimpurities; a product recovery means for recovering said liquid storedin said lower space outside the rectifying the column in the form ofhigh purity hydrogen bromide and a cryogenic storage tank outside saidrectifying column, wherein said product recovery means is used forsending high purity hydrogen bromide stored in said lower space to saidcryogenic storage tank.
 4. The apparatus for preparing high purityhydrogen bromide according to claim 3, wherein a heat exchanger isdisposed at a level higher than the liquid surface inside said cryogenicstorage tank and hydrogen bromide gas generated is cooled to atemperature in the range of -15° C. to -20° C. to condense.
 5. Anapparatus for preparing high purity hydrogen bromide, comprising:arectifying column, comprising a longitudinal pressure vessel which isdivided into a lower space, a lower rectifying section in which pluralstages of rectifying plates are disposed, an intermediate space, anupper rectifying section in which plural stages of rectifying plates aredisposed, and an upper space, which are positioned in the ordermentioned from the bottom toward the top; means for supplying a rawmaterial consisting of hydrogen bromide and impurities having boilingpoints lower than that of hydrogen bromide, into said intermediatespace; a first heat exchanger for cooling and condensing part of anuncondensed gas stored in said upper space; a second heat exchanger forheating and evaporating part of a liquid stored in said lower space; ameans for discharging gas stored in said upper space outside therectifying column in the form of gas rich in impurities; a productrecovery means for recovering said liquid stored in said lower spaceoutside the rectifying column in the form of high purity hydrogenbromide, said second heat exchanger being disposed outside said lowerspace and used for introducing said liquid stored in said lower spaceand evaporating it by exchanging heat with the atmosphere and the gasgenerated is returned in said lower space and a third heat exchangerwhich is disposed in said lower space wherein said means for supplying araw material is used for supplying a raw material to said intermediatespace by way of a flow passage located on a heating medium side of saidthird heat exchanger.
 6. An apparatus for preparing high purity hydrogenbromide, comprising:a rectifying column, housed in a thermal insulationcontainer, comprising a longitudinal pressure vessel which is dividedinto a lower space, a lower rectifying section in which plural stages ofrectifying plates are disposed, an intermediate space, an upperrectifying section in which plural stages of rectifying plates aredisposed, and an upper space, which are positioned in the ordermentioned from the bottom toward the top; means for supplying a rawmaterial consisting of hydrogen bromide and impurities having boilingpoints lower than that of hydrogen bromide, into said intermediatespace; a first heat exchanger for cooling and condensing part of anuncondensed gas stored in said upper space; a second heat exchanger forheating and evaporating part of a liquid stored in said lower space; ameans for discharging gas stored in said upper space outside therectifying column in the form of gas rich in impurities; a productrecovery means for recovering said liquid stored in said lower spaceoutside the rectifying column in the form of high purity hydrogenbromide and wherein said first heat exchanger is disposed inside saidupper space and used for condensing said uncondensed gas stored in saidupper space by exchanging heat with a refrigerant located outside saidthermal insulation container.
 7. An apparatus for preparing high purityhydrogen bromide, comprising:a rectifying column, comprising alongitudinal pressure vessel which is divided into i) a lower space, ii)a lower rectifying section in which plural stages of rectifying platesare disposed, iii) an intermediate space, iv) an upper rectifyingsection in which plural stages of rectifying plates are disposed, and v)an upper space, which are positioned in the order mentioned from thebottom toward the top; vi) means for supplying a raw material consistingof hydrogen bromide and impurities having boiling points lower than thatof hydrogen bromide, into said intermediate space; vii) a first heatexchanger for cooling and condensing part of an uncondensed gas storedin said upper space; viii) a second heat exchanger which is disposedoutside said lower space and used for introducing said liquid stored insaid lower space and evaporating it by exchanging heat with theatmosphere and wherein the gas generated is returned in said lowerspace; ix) a third heat exchanger which is disposed in said lower spacewherein said means for supplying a raw material is used for supplying araw material is used for supplying a raw material to said intermediatespace by way of a flow passage located on a heating medium side of saidthird heat exchanger; x) means for discharging gas stored in said upperspace outside the rectifying column in the form of gas rich inimpurities; and xi) product recovery means for recovering said liquidstored in said lower space outside the rectifying column in the form ofhigh purity hydrogen bromide.
 8. An apparatus for preparing high purityhydrogen bromide, comprising:a rectifying column, comprising alongitudinal pressure vessel which is divided into i) a lower space, ii)a lower rectifying section in which plural stages of rectifying platesare disposed, iii) an intermediate space, iv) an upper rectifyingsection in which plural stages of rectifying plates are disposed, and v)an upper space, which are positioned in the order mentioned from thebottom toward the top; vi) means for supplying a raw material consistingof hydrogen bromide and impurities having boiling points lower than thatof hydrogen bromide, into said intermediate space; vii) a first heatexchanger for cooling and condensing part of an uncondensed gas storedin Said upper space; viii) a second heat exchanger for heating andevaporating pat of a liquid stored in said lower space; ix) means fordischarging gas stored in said upper space outside the rectifying columnin the form of gas rich in impurities; and x) product recovery means forrecovering said liquid stored in said lower space outside the rectifyingcolumn in the form of high purity hydrogen bromide, and xi) cryogenicstorage means.
 9. The apparatus of claim 8, wherein a heat exchanger isdisposed at a level higher than the liquid surface inside the cryogenicstorage tank and hydrogen bromide gas generated is cooled to atemperature in the range of -15° C. to -20° C. to condense.
 10. Theapparatus of claim 8, wherein said cryogenic storage means is a tank.